This invention generally relates to a water pump and more particularly, this invention pertains to a water pump which compulsorily circulates cooling water of an engine for automobile.
A conventional water pump is disclosed in for example, a Japanese Patent Application Publication published as Toku-Kai-Hei 10(1998)-266857. This water pump includes a body, a fixing member to which the body is fixed hermetically via a metal gasket, and an impeller. The impeller is supported rotatably by the body and housed in a vortex chamber formed in the fixing member. Further, the impeller has a circular plate with which the impeller is inserted and blades which extend radially on the body side of the circular plate and project from the circular plate. The metal gasket extends so as to keep a predetermined axial distance between an end part of the body side of the blade and an inner peripheral portion of the metal gasket.
In this conventional water pump, the metal gasket functions so that the gasket separates an intake passage (low pressure side) from a delivery passage (high pressure side) and the axial distance between the blades of the impeller and the metal gasket is kept to maintain a stable delivery performance of the water pump.
Accordingly, high rigidity is needed to be durable against a large pressure difference between the intake passage and the delivery passage.
Meanwhile, flexibility is also needed to form a bead or a folded rib etc. on the metal gasket for ensuring sealing function and improving surface pressure, so the metal gasket needs to be formed of a thin metal plate etc.
However, the metal gasket formed of the thin metal plate has difficulty in compatibility between the sealing function and the high rigidity. And the metal gasket formed of many layers of the thin metal gasket has possibility that deformation and peeling may occur by the pressure difference between the intake passage and the delivery passage.
Now therefore, a technical object of this present invention is providing the water pump ensuring the sealing function as well as the dividing function.
According to an aspect of the present invention, a water pump includes a body, a fixing member to which the body is fixed hermetically via a gasket, and an impeller which is fixed to an end part of a shaft supported rotatably by the body and housed in a vortex chamber formed in the body or in the fixing member. Further, the impeller has a circular plate into which the end part of the shaft is inserted and a plurality of blades radially provided on the circular plate at one side facing the fixing member or the other side facing the body and project from the circular plate to the fixing member side or the body side.
In the foregoing water pump, the gasket has an intermediate plate with high rigidity and metal gaskets disposed between the intermediate plate and the body, and between the intermediate plate and the fixing member for sealing. The intermediate plate extends in radial direction to keep a predetermined axial distance between an inner peripheral portion of the intermediate plate and an end part of the blades facing to the fixing member or to the body.
According to another aspect of the present invention, the gasket includes a primary bore and a secondary bore. The primary bore is formed opposite to the blades of the impeller with a predetermined axial distance between an inner peripheral portion of the primary bore and the end part of the blades facing to the fixing member or to the body. And the secondary bore communicates with an intake passage or a delivery passage. Consequently, a flow passage is formed between a part dividing the primary bore from the secondary bore and the body or the fixing member.